Many current integrated circuits are formed as multiple dice on a common wafer. After the basic process steps to form the circuits on the dice are complete, the individual die are singulated from the wafer. The singulated die are then usually mounted to structures, such as circuit boards, or packaged in some form of enclosure.
One frequently-used package consists of a substrate upon which a die is mounted. The upper surface of the substrate includes electrical interconnects. The die is manufactured with a plurality of bond pads. A collection of solder joints are provided between the bond pads of the die and the substrate interconnects to establish ohmic contact. After the die is mounted to the substrate, a lid is attached to the substrate to cover the die. Some conventional integrated circuits, such as microprocessors, generate sizeable quantities of heat that must be transferred away to avoid device shutdown or damage. The lid serves as both a protective cover and a heat transfer pathway.
Stacked dice arrangements involve placing or stacking one or more semiconductor chips on a base semiconductor chip. In some conventional variants, the base semiconductor chip is a high heat dissipating device, such as a microprocessor. The stacked chips are sometimes memory devices. So-called 2.5D stacking involves placing two chips side-by-side on an interposer, while 3D stacking involves stacking one or more chips on an underlying chip. The stack of chips is placed on an underlying board.